Infection: Infectious Mononucleosis
Infection: Infectious Mononucleosis
Infectious mononucleosis is a highly contagious disease caused by the Epstein-Barr virus (EBV) and spread primarily by contact with the saliva of an infected person. Although the disease is sometimes known as the kissing disease because of the role of saliva in spreading the infection, mononucleosis can also be spread through blood and genital secretions (although these forms of transmission are very rare).
EBV is a very common virus worldwide; most people become infected with it at some point in their lives. Many people become infected with the virus and never develop noticeable symptoms. Those who do develop symptoms typically experience about two weeks of fever, sore throat, and swollen lymph nodes in the neck, throat, or armpits. Although mononucleosis is not a major threat to health, it is a common cause of absence from school or work in teenagers and young adults because it can lead to weeks or months of fatigue and lowered energy.
In the United States, mononucleosis is most common in teenagers and young adults; it is more common in younger children in developing countries. People in any age group can get the disease if they are exposed, however. As many as 95 percent of American adults between thirty-five and forty years of age have been infected, although not all of these have had the symptoms of the illness. When infection with EBV occurs during adolescence or young adulthood, it causes infectious mononucleosis between 35 and 50 percent of the time.
Males and females are equally likely to get mononucleosis, as are people of all races and ethnic groups.
Infectious mononucleosis is caused by the Epstein-Barr virus, or EBV. The virus is normally transmitted by contact with the saliva of an infected person; it is not ordinarily transmitted through the air. The virus takes about four to six weeks to incubate, and thus infected persons can spread the disease to others over a period of several weeks. After entering the patient's mouth and upper throat, the virus infects B cells, which are a certain type of white blood cell produced in the bone marrow. The infected B cells are then carried into the lymphatic system, where they affect the liver and spleen and cause the lymph nodes to swell and
enlarge. The infected B cells are also responsible for the fever, swelling of the tonsils, and sore throat that characterize mononucleosis.
After the symptoms of mononucleosis go away, the EBV virus remains in a few cells in the patient's throat tissues or blood for the rest of the person's life. The virus occasionally reactivates and may appear in samples of the person's saliva, it does not cause new symptoms of illness, it may be transmitted (given) to a susceptible person. Mononucleosis does not cause any problems during pregnancy, such as miscarriages or birth defects.
The primary symptoms of mononucleosis are fever, sore throat, and swollen lymph nodes in the throat, armpit, or neck. Other common symptoms include:
- Swelling or enlargement of the spleen or liver
- General discomfort and mild muscle aches
- Sleepiness and fatigue
- Loss of appetite
- Skin rash
- Swollen tonsils or a yellowish coating on the tonsils
- Night sweats
Less common symptoms of mononucleosis that some patients experience include:
- Stiff neck
- Sensitivity to light
- Shortness of breath and chest pain
The diagnosis of mononucleosis is usually based on the results of blood tests combined with the doctor's examination of the patient's throat and neck. The doctor will also tap on or feel the patient's abdomen to see whether the liver and spleen have become enlarged.
A patient infected by EBV will have an increased number of certain white blood cells in the blood sample called atypical lymphocytes, and antibodies to the Epstein-Barr virus. These antibodies can be detected
by a test called the monospot test, which gives results within a day but may not be accurate during the first week of the patient's illness. Another type of blood test for EBV antibodies takes longer to perform but gives more accurate results within the first week of symptoms.
There is no cure for mononucleosis because it is caused by a virus; it cannot be treated by antibiotics. Treatment consists of self-care at home until the symptoms go away. Patients should rest in bed if possible and drink plenty of fluids. Non-aspirin pain relievers like Advil or Tylenol can be taken to bring down the fever and relieve muscle aches and pains. Throat lozenges or gargling with warm salt water may help ease the discomfort of a sore throat.
Because mononucleosis can affect the spleen, patients should avoid vigorous exercise or contact sports for at least one month after the onset of symptoms or until the spleen returns to its normal size. This precaution will lower the risk of rupture of the spleen.
Mononucleosis rarely causes serious complications. In most patients, the fever goes down in about ten days, but fatigue may last for several weeks or months. Some people do not feel normal again for about three months. A patient who feels sick longer than four months, however, should go back to the doctor to see whether they have another disease or disorder in addition to mononucleosis. In some cases, the patient is diagnosed with chronic fatigue syndrome or CFS. The Epstein-Barr virus does not cause CFS; however, it appears to make some patients with mononucleosis more susceptible to developing chronic fatigue syndrome.
One way to speed complete recovery from infectious mononucleosis is to get plenty of rest early in the disease; the more rest patients get at the beginning, the more quickly they recover.
Severe complications of mononucleosis are unusual but may include rupture of the spleen, which occurs in 0.5 percent of patients—almost all of them males who returned to sports too quickly. Airway obstruction may develop in one patient per thousand, most often a small child. This complication can be treated with steroid medications. Between 1 and 3 percent of patients may develop a form of anemia that can also be treated with steroids.
There is no vaccine that can prevent mononucleosis. In addition, the fact that many people can be infected with the virus and transmit it to others without having symptoms of the disease means that mononucleosis is almost impossible to prevent. The best precautionary measure is for patients who have been diagnosed with mono to avoid kissing, or other close personal contact with, others and to wash their drinking glasses, food dishes, and eating utensils separately from those of other family members or friends for several days after the fever goes down. It is not necessary for people with mono to be completely isolated from other people, however.
Because the Epstein-Barr virus remains in the body after the symptoms of mononucleosis go away, people who have had the disease should not donate blood for at least six months after their symptoms started.
As of 2008 researchers were working on a vaccine against EBV. In December 2007 the Journal of Infectious Diseases reported that a vaccine developed in Belgium shows promise in preventing mononucleosis. The vaccine must undergo further clinical trials, however, before it can be definitely shown to be effective and licensed for use in the United States.
SEE ALSO Chronic fatigue syndrome
WORDS TO KNOW
Anemia : A condition in which there are not enough red cells in the blood or enough hemoglobin in the red blood cells.
Jaundice : A yellowish discoloration of the skin and whites of the eyes caused by increased levels of bile pigments from the liver in the patient's blood.
Decker, Janet. Mononucleosis. Philadelphia: Chelsea House Publishers, 2004.
Hoffmann, Gretchen. Mononucleosis. New York: Marshall Cavendish Benchmark, 2006.
Marcovitz, Hal. Infectious Mononucleosis. Detroit, MI: Lucent Books, 2008.
American Academy of Family Physicians. “Patient Information: Things to Know about Infectious Mononucleosis.” American Family Physician, October 1, 2004. Available online at http://www.aafp.org/afp/20041001/1289ph.html (accessed June 6, 2008).
Baragona, Steve. “Vaccine Shows Promise in Preventing Mono.” News release, Journal of Infectious Diseases, December 10, 2007. Available online at http://idsociety.org/Content.aspx?id=8728 (accessed June 6, 2008).
Mayo Clinic. Mononucleosis. Available online at http://www.mayoclinic.com/health/mononucleosis/DS00352 (accessed June 5, 2008).
National Center for Infectious Diseases. Epstein-Barr Virus and Infectious Mononucleosis. http://www.cdc.gov/ncidod/diseases/ebv.htm (accessed June 6, 2008).
TeensHealth. Mononucleosis. Available online at http://www.kidshealth.org/teen/infections/common/mononucleosis.html (accessed June 6, 2008).